Primate intelligence and social behaviour Introduction Most primates spend their lives in large social groups and the social brain hypothesis posits that selection has favoured larger brains and more complex cognitive capacities as a means to cope with the challenge of social life (Silk 2007) Research in the field and laboratory shows that sophisticated social cognition underlies social behavior in primate groups. Social behaviour is behaviour and interactions that takes place between organisms of the same species. There are many different levels of social behaviour. The “simplest” or lowest forms of social behaviour are those which specific biological processes account directly for the behaviour. These are biological behaviours, of which there are three levels (the taxis, biotaxis and biosocial) the biosocial level is the level at which the reciprocal simulative function of other organisms is the source of the groups behaviour. The higher levels of social behaviour are those of plastic adaptive adjustments arising through widened learning capacities and the entrance of thinking. These higher levels are psychological behaviours of which there are two levels. The psychotaxis is the level at which behavioural plasticity becomes increasingly important in directing the course of behavioural development, as in the effects of maternal behaviour on the subsequent behaviour or the gorilla. The second psychological level is the psychosocial level where the development of bonds becomes an important factor in determining an organism’s further behaviour (Greenberg, 1988) These two psychological behaviours, the psychotaxis and phsycosocial levels are the levels of social behaviour that are easiest to observe in a zoo setting. I have further broken these levels up into further categories, these are; Social observation: individuals watching one another Mother and infants: this is the basic social group for many primates. Mother infant bonding is essential to teach the infant how to interact properly as an adult. Dominance: Primates and animals that live in groups tend to form “dominance hierarchies” the rank is learned through play, agnostic interactions and affiliative interactions. Grooming: this is an important affiliative mechanism and is used to strengthen links Communication: this ncludes scents, body postures, gestures, vocalisations Play: attempts to define play behaviour has been historically tricky (Pellengrini 2005) Cooperative feeding: individuals feeing together The aim of this study is to test the hypothesis that “more ‘advanced’ primates make the most use of social behaviour” so first we must look at how we decide what makes a primate more advanced or more intelligent than another and also look at the emergence of intelligence. The social intelligence hypothesis was developed to explain the evolution of primate intelligence and suggests that life in complex social environments was the primary selective pressure for primate cognitive evolution and for enlarged brains (Maclean 2008). It has been suggested that “intelligence” and brain volume are linked but it remains largely untested. A study by Reader and Laland showed there to be a positive correlation between social learning, innovation and tool use and species’ relative and absolute “executive” brain volumes. Reader and Laland 2002) Also, relative neocortex size is positively correlated with social group size in primates.